When glass, and more particularly a windshield, is struck by an object or projectile such as a rock, the outer glass pane is likely to be damaged. As is well known in the prior art, a shatterproof windshield is composed of an intermediate plastic laminate which bonds an outer glass pane and an inner glass pane together. This combination of glass-plastic laminations absorbs the force of impact, thereby reducing the extent of the damage to the windshield.
Upon impact, glass on the surface of a windshield fractures into a simple crack, or a cone-like formation with damage directed radially therefrom in several directions. When a cone is formed, it normally has a peak on the surface which is often exposed to the atmosphere. The base of the cone typically extends to the bottom of the outer glass pane adjacent the plastic laminate. The sides of this cone, as well as any related fractures that may have formed, are visible to an observer looking through the windshield. Indeed, as light is transmitted through these new interfaces that have formed within the glass, extraneous refraction thereof occurs.
The damage to the windshield, conventionally categorized as a simple crack, a bull's-eye, a star, or a combination thereof, is typically small and confined to the outside glass layer. In the case of bull's-eyes, the fracture planes usually run parallel to the glass surface, sloping downwards. The presence of these fracture planes, which may cover a significant portion of the windshield, can be distracting to the driver and interfere with his line of vision. Furthermore, the presence of fractures, showing as cracks, constitutes points of weakness within the outer glass pane. As is well known to those skilled in the art, such cracks are apt to propagate further, resulting in substantial interference with the driver's vision. Accordingly, to avoid a collision caused by such visual distractions and inhibited line of sight, expensive replacement of the windshield is required.
On the other hand, if this damaged glass could have been repaired prior to the propagation of the cracks by filling the voids within the said damage whereby the fracture planes were properly bonded together, such conventional and costly replacement of the windshield could be avoided.
As is also well known in the prior art, through the use of resins which have refractive indexes substantially the same as that of glass, suitable viscosity, suitable adhesion to glass, and are non-yellowing, it is possible to repair damaged glass and accordingly extend a windshield's life.
Thus, if such resin is injected properly into the damaged glass by one skilled in the art, the interfaces hereinbefore described may be nearly invisible. If such a resin has been applied improperly, however, the damage will still be visible, showing voids, and of course have fracture panes that are not bonded together, thereby resulting in cracked glass which is apt to continue to fail.
It is therefore important to properly inject the resin into the damaged glass. At times this may require halting the injection process to inspect the break and then injecting more resin after inspection. In conventional apparatus, this requires removal of the bridge supporting the injector from the glass and repositioning of the bridge after inspection. When repairing numerous breaks per day, removing the bridge from the glass for inspection results in significant lost time. It is highly desirable to provide a bridge and injection apparatus which can be accurately positioned on the break eliminating the need for further removing and repositioning of the entire bridge.
A search of the prior art produced the following patents, all of which are issued in the United States.
U.S. Pat. Nos. PA1 3,562,366 PA1 4,047,863 PA1 4,597,727 PA1 4,814,185 PA1 4,919,602 PA1 4,995,798
It is submitted that these patents do not show the key features such as the position indicator of the present invention.